Some websites’ login forms have unusual characteristics that require special handling if you use LastPass.

LOGIN FORMS WITH WEIRDO CODING
Some websites’ login forms have unusual coding that don’t play well with LastPass. For example, on one site if I let LastPass fill in my credentials normally, logging in would fail with an incorrect credentials error. Yet if I had LastPass copy my username to the clipboard and paste it into the username field, then do the same with the password, then I could log in without error.

For such websites it’s best to force-save the site with the “Save All Entered Data” feature. To do this, open the troublesome website’s login page. Manually enter your credentials but don’t log in. Click on the LastPass icon and select Tools – Save All Entered Data. An Add Site window will appear. Give the new site a unique name and save it; the Add Site window will close. Back on the troublesome website’s login page, log in, log out, and close the browser.

To check your work, reopen the browser and use LastPass to go to the troublesome website. LastPass should log you in without problem.

LOGIN FORMS NEED STUFF THAT LASTPASS CAN’T SAVE
Some websites’ login forms require information that by its nature cannot be saved in LastPass. For example, a form might have not only the usual username and password field but also a captcha. Another login form might require you to append a token to your password in the form’s password field.

To deal with this, don’t let LastPass automatically log you in. Consider this advice from the LastPass FAQ:

When launching sites directly from the LastPass Icon (drop down menu) or directly from the local Vault, the expected behavior for LastPass is to autofill and auto log into the site, even if a Never option has been enabled for it.

You will need to manually visit the page or use the right-click context “Go to URL” option when in the vault in order for LastPass to not autofill/autologin.